Height adjustment mechanism suitable for a footring

ABSTRACT

A mechanism for vertically adjusting a component on a shaft has a collet sleeve riding on the shaft. A spiral track of the component&#39;s hub receives a radially outwardly projecting pin on the collet sleeve. The outer surface of the collet sleeve and the inner surface of the hub are tapered so that the hub can rotated one direction to advance the hub on the collet sleeve and compress the collet sleeve onto the shaft to frictionally lock the collet sleeve to the shaft. Because the hub is joined to the collet sleeve by the pin, this also locks the vertical position of the component. Conversely, the hub can be oppositely rotated to release the compression of the collet sleeve so that the collet sleeve, and therefore the vertical component, is slidable on the shaft.

BACKGROUND

This invention relates to a mechanism for adjusting the vertical heightof a component, such as the vertical height of a footring of a seat.

A variety of footring adjustment mechanisms are known. For example, U.S.Pat. No. 6,695,407 issued Feb. 24, 2004 to Lin discloses a footring witha cam attached to the hub of the footring that may be rotated toselectively lock the footring on its supporting shaft. U.S. Pat. No.8,297,563 issued Oct. 30, 2012 to Tsai discloses a footring with athreaded hub that threads to an externally threaded collet sleeve toselectively lock the footring on its supporting shaft.

Another height adjustment mechanism suitable for use with a footringwould be advantageous.

SUMMARY

When assembled, a mechanism for vertically adjusting a component on ashaft has a collet sleeve riding on the shaft. The collet sleeve has oneof a radially outwardly projecting pin and a track and the hub of thecomponent has the other of the pin and the track. The track receives thepin and has a first pin stop axially spaced from a second pin stop.Either or both of the outer surface of the collet sleeve and the innersurface of the hub are tapered such that when the hub is moved so thatrelative movement between the pin and track moves the pin to the firstpin stop, the hub is advanced on the collet sleeve to compress thecollet sleeve onto the shaft to frictionally lock the collet sleeve tothe shaft. Because the hub is joined to the collet sleeve by the pin,this also locks the vertical position of the component. Conversely, whenthe hub is moved so that relative movement between the pin and trackmoves the pin to the second stop, the hub is retracted on the colletsleeve to release compression of the collet sleeve so that the colletsleeve is slidable on the shaft and the position of the verticalcomponent on the shaft can be adjusted.

In an aspect, there is provided a mechanism for vertically adjusting acomponent on a shaft, said component having a hub receiving said shaft,said mechanism comprising: a collet sleeve for riding on said shaft,said collet sleeve having one of a radially outwardly projecting pin anda track; a hub sleeve for attachment to a hub of said component, saidhub sleeve having another of said pin and said track; said track forreceiving said pin, said track having a first pin stop and a second pinstop, said second pin stop axially spaced from said first pin stop; atleast one of an outer surface of said collet sleeve and an inner surfaceof said hub sleeve tapered such that when said hub sleeve is moved sothat relative movement between said pin and track moves said pin to saidfirst pin stop, said hub sleeve is advanced on said collet sleeve tocompress said collet sleeve onto said shaft to frictionally lock saidcollet sleeve to said shaft and when said hub sleeve is moved so thatrelative movement between said pin and track moves said pin to saidsecond stop, said hub sleeve is retracted on said collet sleeve torelease compression of said collet sleeve so that said collet sleeve isslidable on said shaft.

In another aspect, there is provided a footring adjustment mechanismcomprising: a collet sleeve for riding on an upright shaft, said colletsleeve having a radially outwardly projecting pin; a hub sleeve forattachment to a hub of said footring, said hub sleeve having a track forreceiving said pin, said track having a spiral track section extendingbetween a first pin stop and a second pin stop so that said first pinstop is above said second pin stop; at least one of an outer surface ofsaid collet sleeve and an inner surface of said hub sleeve tapered suchthat when said hub sleeve is rotated so that relative movement betweensaid pin and track moves said pin along said spiral track section tosaid first pin stop, said hub sleeve is advanced downwardly on saidcollet sleeve to compress said collet sleeve onto said shaft tofrictionally lock said collet sleeve to said shaft and when said hubsleeve is rotated so that relative movement between said pin and trackmoves said pin along said spiral track section to said second stop, saidhub sleeve is retracted upwardly on said collet sleeve to releasecompression of said collet sleeve so that said collet sleeve is slidableon said shaft.

In a further aspect, there is provided a seat having an adjustablefootring comprising: a support shaft; a collet sleeve riding on saidsupport shaft, said collet sleeve having a radially outwardly projectingpin; a hub of said footring extending about said collet sleeve, said hubhaving a track receiving said pin, said track having a spiral tracksection extending between a first pin stop and a second pin stop so thatsaid first pin stop is above said second pin stop; at least one of anouter surface of said collet sleeve and an inner surface of said hubsleeve tapered such that when said hub sleeve is rotated so that saidspiral section of said track moves along said pin to said first pinstop, said hub sleeve is advanced downwardly on said collet sleeve tocompress said collet sleeve onto said shaft to frictionally lock saidcollet sleeve to said shaft and when said hub sleeve is rotated so thatsaid spiral section of said track moves along said pin to said secondpin stop, said hub sleeve is retracted upwardly on said collet sleeve torelease compression of said collet sleeve so that said collet sleeve isslidable on said shaft.

Other features and advantages will become apparent from the followingdescription in conjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In the figures which illustrate an example embodiment of the invention:

FIG. 1 is an exploded perspective view of a portion of a chair with aheight adjustment mechanism for a footring in accordance with anembodiment;

FIG. 2 is a magnified view of the area designated FIG. 2 in FIG. 1;

FIG. 3 is an exploded, and partially cross-sectioned, side view of aportion of a chair with a height adjustment mechanism for a footring inaccordance with the embodiment of FIG. 1;

FIG. 4 is a partially sectioned side view of the chair portion of FIG. 3shown in an assembled state;

FIG. 5 is a magnified view of the area designated FIG. 5 in FIG. 4;

FIG. 6A is a perspective view of the collet sleeve;

FIG. 6B is a side view of the collet sleeve;

FIG. 6C is a top view of the collet sleeve;

FIG. 6D is a cross-sectional view of the collet sleeve along the lines7D-7D of FIG. 7B;

FIG. 7A is a perspective view of a hub sleeve half;

FIG. 7B is a side view of FIG. 7A;

FIG. 7C is a top view of FIG. 7A;

FIG. 7D is a bottom view of FIG. 7A;

FIG. 8A is a perspective view of an assembled hub sleeve;

FIG. 8B is a top view of FIG. 8A;

FIG. 8C is a bottom view of FIG. 8A; and

FIGS. 9A and 9B are schematic views showing operation of the heightadjustment mechanism.

DETAILED DESCRIPTION

Referencing FIGS. 1 to 4, a chair 10 (FIG. 3) has a gas control cylinder12 with a cylinder body acting as a support shaft 20. The support shaft20 is mounted in a wheeled base 16 and the piston shaft 14 of the gascontrol cylinder supports a chair control mechanism 22 (FIG. 3) to whichthe seat 24 (FIG. 3) of the chair is attached. The chair has footring 26supported on the shaft 20 by height adjustment mechanism 30. The heightadjustment mechanism 30 has a collet sleeve 40 and a hub sleeve 50.

With reference to FIGS. 6A to 6D, the collet sleeve 40 is a resilientplastic ring with a series of axially directed slots 42 extending fromthe upper edge 44 of the ring and a pair of opposed, radially outwardlydirected, pins 46. The ring tapers from its base 43 to its upper edge44. The sleeve has a rectangular depression 48 between each pair ofslots. A resilient pad 49 (FIG. 3) is received by each rectangulardepression 48 and may be glued in place. As indicated by FIG. 4, thecollet sleeve 40 with resilient friction enhancing pads 49 rides onshaft 20.

With reference to FIGS. 7A to 7D and 8A to 8C along with FIG. 2, the hubsleeve is a pair of hub halves 50 a, 50 b with pegs 52 and holes 54which allow the halves to be mated. The hub sleeve has a basal annularridge 56 with holes 58 that align with holes 62 in the hub 60 of thefootring 26 to allow screws 64 to affix the hub sleeve 50 into the hubof the footring. Each hub sleeve half has a track 70 formed in it forreceiving one of the pins 46 of the collet sleeve. The inner surface 67of the hub sleeve 50 tapers from its base 66 to its upper edge 68. Withspecific reference to FIG. 7C, track 70 has a spiral track section 72, afirst, upper, end portion 74 which extends circumferentially at aconstant axial position from the upper end of the spiral track section,and a second, lower, end portion 76 which extends from the lower end ofthe spiral track section. The first end portion terminates at a firstpin stop 80 and defines a detent 82 spaced from the first pin stop. Thesecond end portion terminates at a second pin stop 84 and defines adetent 86 spaced from the second pin stop. The track also has an axiallydirected track section 88 extending to the spiral track section 72.

In assembly of the chair, the gas control cylinder 12 is inserted intothe base 16 and the collet sleeve 40 with attached pads 48 is slid overshaft 20 of the gas control cylinder so that the slots 42 are upwardlydirected. The hub sleeve halves 50 a, 50 b are mated to form the hubsleeve and the hub sleeve is affixed to the hub 60 of the footring withscrews 64. Next the footring with the attached hub sleeve is slid ontothe shaft 20 which the axially directed track sections 88 aligned withthe pins 46 of the collet sleeve 40 so that the pins slide along theaxially directed track sections 88 to the spiral track sections 72, asshown in FIG. 4. Now a chair control mechanism 22 can be installed onthe shaft 20 and a seat attached to the chair control mechanism tocomplete the chair.

In operation, if the footring 26 and hub sleeve 50 are in the positionillustrated in FIG. 9A, the hub sleeve tracks 70 are oriented so that apin 46 of the collet sleeve is at the first pin stop 80 of each trackand the hub sleeve is positioned low over the collet sleeve. In thisposition, due to the taper of the collet sleeve and inner surface of thehub sleeve, the hub sleeve compresses the collet sleeve so that itsslots 42 have a reduced width, as shown at A in FIG. 9A. When in thiscompressed state, the collet sleeve, aided by the friction enhancingpads 49, is firmly frictionally locked to shaft 20. And because of thepin to track connection between the collet sleeve and the hub sleeve,this means the vertical height of the footring 26 is fixed.

From the position illustrated in FIG. 9A, the footring 26 may be rotatedin a counterclockwise direction with sufficient force to overcome thetrack detents 82 to rotate the hub sleeve 50, and hence the tracks 70 ofthe hub sleeve, counterclockwise. This causes the footring to moveupwardly relative to the collet sleeve as the spiral section 72 of eachtrack rides along the pins 46 of the collet sleeve 40 until the pinstops 84 of the tracks abut the pins 46, as illustrated in FIGS. 5 and9B. In this position, the detent 86 of each track assists in retainingthe pins 46 so that the footrest is restrained from rotating clockwise.Because of the taper of the collet sleeve and the inner surface of thehub sleeve, when the hub sleeve is withdrawn upwardly relative to thecollet sleeve, the collet sleeve is uncompressed and the slots 42 of thecollet sleeve return to their relaxed width, B. With the collet in arelaxed state, it is no longer tightly frictionally locked to the shaft20. Consequently, a user, by applying an upward or downward force on thefootring, can adjust the position of the footring on shaft 20. Once thefootring has been adjusted to a desired position, the footring can berotated clockwise. This moves the tracks along the pins, advancing thehub sleeve on the collet sleeve to compress the collet sleeve as thespiral section of the tracks move along the pins. Once the tracks moveso that the pins enter the upper end portion 74 of the tracks 70,continued clockwise rotation will no longer advance the hub sleeve onthe collet sleeve but will return the hub sleeve to the positionillustrated in FIG. 9A whereat the pin stops 80 of the tracks abut thepins 46 and the collet sleeve and hub sleeve with footring are locked intheir new vertical position.

While the track has been described as being formed in the hub sleeve 50and the pins 46 as projecting from the collet sleeve 40, equally thetrack could be formed in the collet sleeve and the pins on the hubsleeve. Also, while the hub sleeve is described as a separate part thatis joined to the hub of the footring, a footring could instead be formedwith a hub having a track such that a separate hub sleeve is not needed.

While the vertical adjustment mechanism has been described for afootring of a chair, equally the mechanism could be used for a footringof a stool or, indeed, for any other component riding on a shaft.

Other modifications will be apparent to those skilled in the art and,therefore, the invention is defined in the claims.

What is claimed is:
 1. A mechanism for vertically adjusting a componenton a shaft, said component having a hub receiving said shaft, saidmechanism comprising: a collet sleeve for riding on said shaft, saidcollet sleeve having one of a radially outwardly projecting pin and atrack; a hub sleeve for attachment to a hub of said component, said hubsleeve having another of said pin and said track; said track forreceiving said pin, said track having a first pin stop and a second pinstop, said second pin stop axially spaced from said first pin stop; atleast one of an outer surface of said collet sleeve and an inner surfaceof said hub sleeve tapered such that when said hub sleeve is moved sothat relative movement between said pin and track moves said pin to saidfirst pin stop, said hub sleeve is advanced on said collet sleeve tocompress said collet sleeve onto said shaft to frictionally lock saidcollet sleeve to said shaft and when said hub sleeve is moved so thatrelative movement between said pin and track moves said pin to saidsecond stop, said hub sleeve is retracted on said collet sleeve torelease compression of said collet sleeve so that said collet sleeve isslidable on said shaft.
 2. The mechanism of claim 1 wherein said trackhas a first spiral track section.
 3. The mechanism of claim 2 whereinsaid track has a first end portion extending circumferentially at aconstant axial position from a first end of said first track section,said first end portion terminating at said first pin stop.
 4. Themechanism of claim 3 wherein said first end portion defines a detentspaced from said first pin stop.
 5. The mechanism of claim 4 whereinsaid track has a second end portion extending from a second end of saidfirst track section, said second end portion terminating at said secondpin stop.
 6. The mechanism of claim 5 wherein said second end portiondefines a detent spaced from said second pin stop.
 7. The mechanism ofclaim 2 wherein said track has a second track section extending axiallyto said first track section for permitting admission of said pin to saidfirst track section during assembly.
 8. The mechanism of claim 2 whereinsaid hub sleeve comprises two separate sleeve halves.
 9. The mechanismof claim 1 wherein said collet sleeve is a resilient plastic ring with aplurality of axial slots extending from one end.
 10. The mechanism ofclaim 7 further comprising a plurality of resilient pads lining aninterior surface of said collet sleeve.
 11. The mechanism of claim 2wherein said pin extends from said collet sleeve and said hub sleeve hassaid track.
 12. A footring adjustment mechanism comprising: a colletsleeve for riding on an upright shaft, said collet sleeve having aradially outwardly projecting pin; a hub sleeve for attachment to a hubof said footring, said hub sleeve having a track for receiving said pin,said track having a spiral track section extending between a first pinstop and a second pin stop so that said first pin stop is above saidsecond pin stop; at least one of an outer surface of said collet sleeveand an inner surface of said hub sleeve tapered such that when said hubsleeve is rotated so that relative movement between said pin and trackmoves said pin along said spiral track section to said first pin stop,said hub sleeve is advanced downwardly on said collet sleeve to compresssaid collet sleeve onto said shaft to frictionally lock said colletsleeve to said shaft and when said hub sleeve is rotated so thatrelative movement between said pin and track moves said pin along saidspiral track section to said second stop, said hub sleeve is retractedupwardly on said collet sleeve to release compression of said colletsleeve so that said collet sleeve is slidable on said shaft.
 13. Themechanism of claim 12 wherein said collet sleeve is a plastic ring witha plurality of axial slots extending from an upper end of said colletsleeve.
 14. The mechanism of claim 12 wherein said track has an upperend portion extending circumferentially at a constant axial positionfrom an upper end of said spiral track section, said upper end portionterminating at said first pin stop.
 15. The mechanism of claim 12wherein said track has an axially directed track section extendingaxially to said spiral track section for permitting admission of saidpin to said spiral track section during assembly.
 16. The mechanism ofclaim 12 wherein said hub sleeve comprises two separate sleeve halves.17. A seat having an adjustable footring comprising: a support shaft; acollet sleeve riding on said support shaft, said collet sleeve having aradially outwardly projecting pin; a hub of said footring extendingabout said collet sleeve, said hub having a track receiving said pin,said track having a spiral track section extending between a first pinstop and a second pin stop so that said first pin stop is above saidsecond pin stop; at least one of an outer surface of said collet sleeveand an inner surface of said hub sleeve tapered such that when said hubsleeve is rotated so that said spiral section of said track moves alongsaid pin to said first pin stop, said hub sleeve is advanced downwardlyon said collet sleeve to compress said collet sleeve onto said shaft tofrictionally lock said collet sleeve to said shaft and when said hubsleeve is rotated so that said spiral section of said track moves alongsaid pin to said second pin stop, said hub sleeve is refracted upwardlyon said collet sleeve to release compression of said collet sleeve sothat said collet sleeve is slidable on said shaft.
 18. The mechanism ofclaim 17 wherein said collet sleeve is a plastic ring with a pluralityof axial slots extending from an upper end of said collet sleeve. 19.The mechanism of claim 18 wherein said track has an upper end portionextending circumferentially at a constant axial position from an upperend of said spiral track section, said upper end portion terminating atsaid first pin stop.
 20. The mechanism of claim 19 wherein said trackhas an axially directed track section extending axially to said spiraltrack section for permitting admission of said pin to said spiral tracksection during assembly.